1. Field of the Invention
The present invention relates to the blowdown piping arrangement installed within the pressure relief system of a nuclear power plant. More specifically, the invention relates to a manifold within the pressure relief system that includes a fluidic device installed therein. The fluidic device provides a low flow resistance to air trapped within the exhaust piping of the relief system and a higher flow resistance to water and/or steam flowing through the pressure relief system piping upstream of the trapped air.
2. Description of Related Art
Nuclear power plants, including both the pressurized water reactor (PWR) design and the boiling water reactor (BWR) design, incorporate systems to prevent overpressurization of the main coolant system. Typically, these pressure relief systems are connected to the main coolant system, and comprise pressure relief valves, of various designs, that are designed to open at a specified pressure setpoint. If the main coolant system pressure reaches the specified setpoint, one or more pressure relief valves open, allowing primary coolant to flow through the valve, thereby lowering the pressure in the main coolant system.
The flow of primary coolant through the pressure relief system piping is directed into a manifold that typically includes one or more exhaust pipes. The exhaust pipes direct the primary coolant into a tank or reservoir, which may be partially filled with water. Moreover, in some plant designs, the exhaust pipes may be submerged, at least partially, into this water to facilitate condensation of the primary coolant discharged by the pressure relief system.
One problem that arises with the above-described conventional pressure relief system is that the air in the manifold and exhaust pipes is first driven out of the manifold and exhaust pipes before the vented primary coolant arrives at the exit of the exhaust pipes. This venting of the air can cause significant dynamic loads in the reservoir or tank, which can lead to damage.
It is therefore an object of the present invention to vent the air in the manifold and exhaust pipes to the surrounding atmosphere and subsequently allow only primary coolant to enter the tank or reservoir.
In one aspect of the present invention, a blowdown manifold for a nuclear power plant comprises a main conduit section, at least one coolant exhaust conduit, and at least one fluidic device. The main conduit section is in fluid communication with a pressure relief system in the nuclear power plant. The coolant exhaust conduit has a first end coupled to the main conduit section and a second end extending into a receptacle. The fluidic device is in fluid communication with the main conduit, and has a first fluid resistance to air and a second fluid resistance, higher than the first fluid resistance, to a fluid other than air.
In another aspect of the invention, a blowdown manifold connected to pressure relief system piping in a nuclear power plant comprises manifold means, exhaust piping means, and dual resistance flow means. The manifold means receives primary coolant flow from the nuclear power plant and directs the flow in a plurality of directions. The exhaust piping means receives the primary coolant from the manifold and directs the primary coolant into a receptacle. The dual resistance flow means presents a first flow resistance to air and a second flow resistance to the primary coolant, wherein the second flow resistance is higher than the first flow resistance.
These and other objects, aspects, advantages and features of the present invention will become more apparent to those skilled in the art when the following detailed description is read in conjunction with the accompanying drawings.